<!DOCTYPE html>
<html lang="en">

<!--head代表网页头部-->
<head>
    <meta charset="UTF-8">
    <title>第一个网页</title>
</head>
<!--body代表网页主体-->
<body>
    <h1>一级标题</h1>
    <h2>二级标题</h2>
    <h3>三级标题</h3>
<br/>

<h4>4级标题</h4>
<h5>5级标题</h5>
<h6>6级标题</h6>
<!--br:换行-->
<br/>
</body>
</html>